Update:
I got new snails two days ago and they were eating my plants. So I threw in a cucumber and let them eat that. My tank was disgusting this morning. Like, green everywhere. My brain hurts thinking of everything I'm going to have to do. So far I've rehomed the troublesome snails (keeping my original one who only likes algae wafers), given the tank a 60% water change and gravel vacuuming and have added in my filter. The water looks slightly better, but if it's not totally gone by tomorrow I'm doing a full cleaning. Stupid snails. I prebought my new Bettas last night, and it's too late to go back on that plan now, as my mother is yelling at me to get in the car... I'll put them further away from the vent, I have some space to do that. One will go in a 1g and the other in a vase or 5g. I'm cutting the plexiglass tomorrow or Sunday. Okay, the tank is clearing up already, I don't think the stress of a full cleaning is necessary, I'll just do a lot of algae scrubbing and clean it again Sunday. Uuuuugh, this feels like torture. Sorry for the whining, aha. Anyways, if anyone has comments or noticed something I said was horribly wrong please, please, please tell me! I just want my fish to be okay :/